This invention relates to a valve excellent in galling-resistant and cavitation erosion-resistant properties.
Heretofore, seat rings of valves used in various plants such as chemical plants and nuclear power plants are welded with a Co-based Cr-W-C-Co alloy which is generally called a Stellite in order to provide them with galling-resistant and cavitation erosion-resistant properties.
However, from the viewpoints of the prevention of exhaustion of cobalt resources and the improvement of safety in the nuclear power plants, researches have been conducted into valve seat rings on which an Ni-based or Fe-based cavitation erosion-resistant and wear-resistant alloy is employed instead of the above-mentioned Stellite, with the intention of inhibiting the emission of cobalt (see D. Ellis and R. L. Squires, "Weld Deposition and Properties of Nickel Based Hardfacing Alloys", Metal Construction, 15 (7) 388-393).
The known Ni-based and Fe-based alloys are, however, poorer in cavitation erosion-resistant and galling-resistant properties as compared with the Co-based Stellite.